Regina George is the most popular girl in the school, she is also the dominant leader of the clique "Plastics" Regina isn't as wealthy as her friend Gretchen Wieners, but is still considerably wealthy. Her home life seems great but her parents don't get along and are "separated but still living together".

Her mom seems to be going through a mid-life crisis and is always trying to be cool and a lot like Regina. The parents don't seem to be paying attention to their other daughter, who is seen watching girls flashing boys on tv and mimicking the act. Regina is wicked in every way, she is very witty and knows how to decieve people. She used to be friends with outcast Janice , but in middle school made up a rumor about Janice being a lesbian. The rumor made Janice go homeschooled and she became a outcast and plotting her revenge on Regina.

Towards the end of the movie Cady has continuously given Regina gronola bars that make you gain weight, but Cady told Regina that she'll lose weight when eating them. So Regina blames Cady for putting together a "Burn Book" that had severely hurtful and personal information about every girl in school, but Regina was the real maker of the book. Then after a all girl meeting in the gymnasium, Regina storms out and Cady runs after her.

They begin arguing and Regina backs into the road and gets run over by the school bus. People say Cady pushed her but that is false, Cady thinks everyone hates her but its made her as popular as Regina and she is voted Prom Queen. At the end Regina is on stage, in a huge embarrasing backbrace, as runnerup Prom Queen. Cady then breaks the crown into peices and shares it with the runnerups and the croud. The plastics split up and go their seperate ways. Regina takes up aggresive sports to release all of her built up anger.